Related
I'm curious if I can assign a variable the value of a specific array index value returned by a function in PHP on one line.
Right now I have a function that returns an associative array and I do what I want in two lines.
$var = myFunction($param1, $param2);
$var = $var['specificIndex'];
without adding a parameter that determines what the return type is, is there a way to do this in one line?
In PHP 5.4, you can do this: $var = myFunction(param1, param2)['specificIndex'];.
Another option is to know the order of the array, and use list(). Note that list only works with numeric arrays.
For example:
function myFunction($a, $b){
// CODE
return array(12, 16);
}
list(,$b) = myFunction(1,2); // $b is now 16
You could add an additional optional parameter and, if set, would return that value. See the following code:
function myFunction($param1, $param2, $returnVal = "")
{
$arr = array();
// your code here
if ($returnVal)
{
return $arr[$returnval];
}
else
{
return $arr;
}
}
Well, I know what references are and when it's use is obvious.
One thing I really can't get is that when it's better to pass function by reference.
<?php
//right here, I wonder why and when
function &test(){
}
To avoid confusion, there're some examples as how I understand the references,
<?php
$numbers = array(2,3,4);
foreach ($numbers as &$number){
$number = $number * 2;
}
// now numbers is $numbers = array(4,6,8);
$var = 'test';
$foo = &var; //now all changes to $foo will be affected to $var, because we've assigned simple pointer
//Similar to array_push()
function add_key(&$array, $key){
return $array[$key];
}
//so we don't need to assign returned value from this function
//we just call this one
$array = array('a', 'b');
add_key($array,'c');
//now $array is ('a', 'b', 'c');
All benefits of using the references are obvious to me, except the use of "passing function by reference",
Question: When to pass function by reference (I've searched answer here, but still can't grasp this one)
Thanks
This is a function that returns by reference -- the term "passing a function by reference" is a bit misleading:
function &test(){
return /* something */;
}
The use cases are pretty much the same as for normal references, which is to say not common. For a (contrived) example, consider a function that finds an element in an array:
$arr = array(
array('name' => 'John', 'age' => 20),
array('name' => 'Mary', 'age' => 30),
);
function &findPerson(&$list, $name) {
foreach ($list as &$person) {
if ($person['name'] == $name) {
return $person;
}
}
return null;
}
$john = &findPerson($arr, 'John');
$john['age'] = 21;
print_r($arr); // changing $john produces a visible change here
See it in action.
In the above example, you have encapsulated the code that searches for an item inside a data structure (which in practice could be a lot more complicated than this array) in a function that can be reused. If you intend to use the return value to modify the original structure itself there's no other option than returning a reference from the function (in this specific case you could also have returned an index into the array, but think about structures that do not have indexes, e.g. graphs).
Do you means Returning References ?
A simple example is:
function &test(&$a){
return $a;
}
$a = 10;
$b = &test($a);
$b++;
// here $a became 11
var_dump($a);
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Multiple returns from function
Is it possible to return 2 results in the same PHP function? One is an array, the other is an integer. Could someone give me an example?
function functest() {
return array(1, "two");
}
list($first,$second) = functest();
There's nothing stopping you from returning whatever type you like from a function. You can return a dictionary with multiple keys, or an array of mixed object types, or whatever. Anything you like.
$arr = array();
$arr[] = $some_object;
$arr[] = 3;
$arr["a_string"] = "foo";
return $arr;
You have several options to simulate multiple return values (the first two, however, are just a kind of wrapping of multiple values into one):
Return an array with the two values: return array($myInt, $myArr); (see e.g. parse_url().)
Create a dedicated wrapper object and return this: return new MyIntAndArrayWrapper($myInt, $myArr);
Add an "output argument" to the function signature: function myFunc(&$myIntRetVal) { ... return $myArr; } (see e.g. preg_match(..., &$matches).)
What about this?
function myfunction() {
//Calculate first result
$arrayresult=...
//Calculate second result
$intresult=...
//Move in with each other . don't be shy!
return array($arrayresult,$intresult)
}
and in the other code
$tmp=myfunction();
$arrayresult=$tmp[0];
$intresult=$tmp[1];
It's totally possible since PHP doesn't use strong typing. Just return the value you want in whatever type you want. A simple example:
function dual($type) {
if ($type === 'integer')
return 4711;
else
return 'foo';
}
You can use several functions on the caller side to see which type you got, for example: gettype, is_int, is_a.
Background
In every other programming language I use on a regular basis, it is simple to operate on the return value of a function without declaring a new variable to hold the function result.
In PHP, however, this does not appear to be so simple:
example1 (function result is an array)
<?php
function foobar(){
return preg_split('/\s+/', 'zero one two three four five');
}
// can php say "zero"?
/// print( foobar()[0] ); /// <-- nope
/// print( &foobar()[0] ); /// <-- nope
/// print( &foobar()->[0] ); /// <-- nope
/// print( "${foobar()}[0]" ); /// <-- nope
?>
example2 (function result is an object)
<?php
function zoobar(){
// NOTE: casting (object) Array() has other problems in PHP
// see e.g., http://stackoverflow.com/questions/1869812
$vout = (object) Array('0'=>'zero','fname'=>'homer','lname'=>'simpson',);
return $vout;
}
// can php say "zero"?
// print zoobar()->0; // <- nope (parse error)
// print zoobar()->{0}; // <- nope
// print zoobar()->{'0'}; // <- nope
// $vtemp = zoobar(); // does using a variable help?
// print $vtemp->{0}; // <- nope
PHP can not access array results from a function. Some people call this an issue, some just accept this as how the language is designed. So PHP makes you create unessential variables just to extract the data you need.
So you need to do.
$var = foobar();
print($var[0]);
This is specifically array dereferencing, which is currently unsupported in php5.3 but should be possible in the next release, 5.4. Object dereferencing is on the other hand possible in current php releases. I'm also looking forward to this functionality!
Array Dereferencing is possible as of PHP 5.4:
http://svn.php.net/viewvc?view=revision&revision=300266
Example (source):
function foo() {
return array(1, 2, 3);
}
echo foo()[2]; // prints 3
with PHP 5.3 you'd get
Parse error: syntax error, unexpected '[', expecting ',' or ';'
Original Answer:
This has been been asked already before. The answer is no. It is not possible.
To quote Andi Gutmans on this topic:
This is a well known feature request
but won't be supported in PHP 5.0. I
can't tell you if it'll ever be
supported. It requires some research
and a lot of thought.
You can also find this request a number of times in the PHP Bugtracker. For technical details, I suggest you check the official RFC and/or ask on PHP Internals.
Well, you could use any of the following solutions, depending on the situation:
function foo() {
return array("foo","bar","foobar","barfoo","tofu");
}
echo(array_shift(foo())); // prints "foo"
echo(array_pop(foo())); // prints "tofu"
Or you can grab specific values from the returned array using list():
list($foo, $bar) = foo();
echo($foo); // prints "foo"
echo($bar); // print "bar"
Edit: the example code for each() I gave earlier was incorrect. each() returns a key-value pair. So it might be easier to use foreach():
foreach(foo() as $key=>$val) {
echo($val);
}
There isn't a way to do that unfortunately, although it is in most other programming languages.
If you really wanted to do a one liner, you could make a function called a() and do something like
$test = a(func(), 1); // second parameter is the key.
But other than that, func()[1] is not supported in PHP.
As others have mentioned, this isn't possible. PHP's syntax doesn't allow it. However, I do have one suggestion that attacks the problem from the other direction.
If you're in control of the getBarArray method and have access to the PHP Standard Library (installed on many PHP 5.2.X hosts and installed by default with PHP 5.3) you should consider returning an ArrayObject instead of a native PHP array/collection. ArrayObjects have an offetGet method, which can be used to retrieve any index, so your code might look something like
<?php
class Example {
function getBarArray() {
$array = new ArrayObject();
$array[] = 'uno';
$array->append('dos');
$array->append('tres');
return $array;
}
}
$foo = new Example();
$value = $foo->getBarArray()->offsetGet(2);
And if you ever need a native array/collection, you can always cast the results.
//if you need
$array = (array) $foo->getBarArray();
Write a wrapper function that will accomplish the same. Because of PHP's easy type-casting this can be pretty open-ended:
function array_value ($array, $key) {
return $array[$key];
}
If you just want to return the first item in the array, use the current() function.
return current($foo->getBarArray());
http://php.net/manual/en/function.current.php
Actually, I've written a library which allows such behavior:
http://code.google.com/p/php-preparser/
Works with everything: functions, methods. Caches, so being as fast as PHP itself :)
You can't chain expressions like that in PHP, so you'll have to save the result of array_test() in a variable.
Try this:
function array_test() {
return array(0, 1, 2);
}
$array = array_test();
echo $array[0];
This is too far-fetched, but if you really NEED it to be in one line:
return index0( $foo->getBarArray() );
/* ... */
function index0( $some_array )
{
return $some_array[0];
}
You could, of course, return an object instead of an array and access it this way:
echo "This should be 2: " . test()->b ."\n";
But I didn't find a possibility to do this with an array :(
my usual workaround is to have a generic function like this
function e($a, $key, $def = null) { return isset($a[$key]) ? $a[$key] : $def; }
and then
echo e(someFunc(), 'key');
as a bonus, this also avoids 'undefined index' warning when you don't need it.
As to reasons why foo()[x] doesn't work, the answer is quite impolite and isn't going to be published here. ;)
These are some ways to approach your problem.
First you could use to name variables directly if you return array of variables that are not part of the collection but have separate meaning each.
Other two ways are for returning the result that is a collection of values.
function test() {
return array(1, 2);
}
list($a, $b) = test();
echo "This should be 2: $b\n";
function test2() {
return new ArrayObject(array('a' => 1, 'b' => 2), ArrayObject::ARRAY_AS_PROPS);
}
$tmp2 = test2();
echo "This should be 2: $tmp2->b\n";
function test3() {
return (object) array('a' => 1, 'b' => 2);
}
$tmp3 = test3();
echo "This should be 2: $tmp3->b\n";
Extremely ghetto, but, it can be done using only PHP. This utilizes a lambda function (which were introduced in PHP 5.3). See and be amazed (and, ahem, terrified):
function foo() {
return array(
'bar' => 'baz',
'foo' => 'bar',
}
// prints 'baz'
echo call_user_func_array(function($a,$k) {
return $a[$k];
}, array(foo(),'bar'));
The lengths we have to go through to do something so beautiful in most other languages.
For the record, I do something similar to what Nolte does. Sorry if I made anyone's eyes bleed.
After further research I believe the answer is no, a temporary variable like that is indeed the canonical way to deal with an array returned from a function.
Looks like this will change starting in PHP 5.4.
Also, this answer was originally for this version of the question:
How to avoid temporary variables in PHP when using an array returned from a function
Previously in PHP 5.3 you had to do this:
function returnArray() {
return array(1, 2, 3);
}
$tmp = returnArray();
$ssecondElement = $tmp[1];
Result: 2
As of PHP 5.4 it is possible to dereference an array as follows:
function returnArray() {
return array(1, 2, 3);
}
$secondElement = returnArray()[1];
Result: 2
As of PHP 5.5:
You can even get clever:
echo [1, 2, 3][1];
Result: 2
You can also do the same with strings. It's called string dereferencing:
echo 'PHP'[1];
Result: H
If it is just aesthetic, then the Object notation will work if you return an object. As far as memory management goes, no temporary copy if made, only a change in reference.
Short Answer:
Yes. It is possible to operate on the return value of a function in PHP, so long as the function result and your particular version of PHP support it.
Referencing example2:
// can php say "homer"?
// print zoobar()->fname; // homer <-- yup
Cases:
The function result is an array and your PHP version is recent enough
The function result is an object and the object member you want is reachable
There are three ways to do the same thing:
As Chacha102 says, use a function to return the index value:
function get($from, $id){
return $from[$id];
}
Then, you can use:
get($foo->getBarArray(),0);
to obtain the first element and so on.
A lazy way using current and array_slice:
$first = current(array_slice($foo->getBarArray(),0,1));
$second = current(array_slice($foo->getBarArray(),1,1));
Using the same function to return both, the array and the value:
class FooClass {
function getBarArray($id = NULL) {
$array = array();
// Do something to get $array contents
if(is_null($id))
return $array;
else
return $array[$id];
}
}
Then you can obtain the entire array and a single array item.
$array = $foo->getBarArray();
or
$first_item = $foo->getBarArray(0);
Does this work?
return ($foo->getBarArray())[0];
Otherwise, can you post the getBarArray() function? I don't see why that wouldn't work from what you posted so far.
You could use references:
$ref =& myFunc();
echo $ref['foo'];
That way, you're not really creating a duplicate of the returned array.
Background
In every other programming language I use on a regular basis, it is simple to operate on the return value of a function without declaring a new variable to hold the function result.
In PHP, however, this does not appear to be so simple:
example1 (function result is an array)
<?php
function foobar(){
return preg_split('/\s+/', 'zero one two three four five');
}
// can php say "zero"?
/// print( foobar()[0] ); /// <-- nope
/// print( &foobar()[0] ); /// <-- nope
/// print( &foobar()->[0] ); /// <-- nope
/// print( "${foobar()}[0]" ); /// <-- nope
?>
example2 (function result is an object)
<?php
function zoobar(){
// NOTE: casting (object) Array() has other problems in PHP
// see e.g., http://stackoverflow.com/questions/1869812
$vout = (object) Array('0'=>'zero','fname'=>'homer','lname'=>'simpson',);
return $vout;
}
// can php say "zero"?
// print zoobar()->0; // <- nope (parse error)
// print zoobar()->{0}; // <- nope
// print zoobar()->{'0'}; // <- nope
// $vtemp = zoobar(); // does using a variable help?
// print $vtemp->{0}; // <- nope
PHP can not access array results from a function. Some people call this an issue, some just accept this as how the language is designed. So PHP makes you create unessential variables just to extract the data you need.
So you need to do.
$var = foobar();
print($var[0]);
This is specifically array dereferencing, which is currently unsupported in php5.3 but should be possible in the next release, 5.4. Object dereferencing is on the other hand possible in current php releases. I'm also looking forward to this functionality!
Array Dereferencing is possible as of PHP 5.4:
http://svn.php.net/viewvc?view=revision&revision=300266
Example (source):
function foo() {
return array(1, 2, 3);
}
echo foo()[2]; // prints 3
with PHP 5.3 you'd get
Parse error: syntax error, unexpected '[', expecting ',' or ';'
Original Answer:
This has been been asked already before. The answer is no. It is not possible.
To quote Andi Gutmans on this topic:
This is a well known feature request
but won't be supported in PHP 5.0. I
can't tell you if it'll ever be
supported. It requires some research
and a lot of thought.
You can also find this request a number of times in the PHP Bugtracker. For technical details, I suggest you check the official RFC and/or ask on PHP Internals.
Well, you could use any of the following solutions, depending on the situation:
function foo() {
return array("foo","bar","foobar","barfoo","tofu");
}
echo(array_shift(foo())); // prints "foo"
echo(array_pop(foo())); // prints "tofu"
Or you can grab specific values from the returned array using list():
list($foo, $bar) = foo();
echo($foo); // prints "foo"
echo($bar); // print "bar"
Edit: the example code for each() I gave earlier was incorrect. each() returns a key-value pair. So it might be easier to use foreach():
foreach(foo() as $key=>$val) {
echo($val);
}
There isn't a way to do that unfortunately, although it is in most other programming languages.
If you really wanted to do a one liner, you could make a function called a() and do something like
$test = a(func(), 1); // second parameter is the key.
But other than that, func()[1] is not supported in PHP.
As others have mentioned, this isn't possible. PHP's syntax doesn't allow it. However, I do have one suggestion that attacks the problem from the other direction.
If you're in control of the getBarArray method and have access to the PHP Standard Library (installed on many PHP 5.2.X hosts and installed by default with PHP 5.3) you should consider returning an ArrayObject instead of a native PHP array/collection. ArrayObjects have an offetGet method, which can be used to retrieve any index, so your code might look something like
<?php
class Example {
function getBarArray() {
$array = new ArrayObject();
$array[] = 'uno';
$array->append('dos');
$array->append('tres');
return $array;
}
}
$foo = new Example();
$value = $foo->getBarArray()->offsetGet(2);
And if you ever need a native array/collection, you can always cast the results.
//if you need
$array = (array) $foo->getBarArray();
Write a wrapper function that will accomplish the same. Because of PHP's easy type-casting this can be pretty open-ended:
function array_value ($array, $key) {
return $array[$key];
}
If you just want to return the first item in the array, use the current() function.
return current($foo->getBarArray());
http://php.net/manual/en/function.current.php
Actually, I've written a library which allows such behavior:
http://code.google.com/p/php-preparser/
Works with everything: functions, methods. Caches, so being as fast as PHP itself :)
You can't chain expressions like that in PHP, so you'll have to save the result of array_test() in a variable.
Try this:
function array_test() {
return array(0, 1, 2);
}
$array = array_test();
echo $array[0];
This is too far-fetched, but if you really NEED it to be in one line:
return index0( $foo->getBarArray() );
/* ... */
function index0( $some_array )
{
return $some_array[0];
}
You could, of course, return an object instead of an array and access it this way:
echo "This should be 2: " . test()->b ."\n";
But I didn't find a possibility to do this with an array :(
my usual workaround is to have a generic function like this
function e($a, $key, $def = null) { return isset($a[$key]) ? $a[$key] : $def; }
and then
echo e(someFunc(), 'key');
as a bonus, this also avoids 'undefined index' warning when you don't need it.
As to reasons why foo()[x] doesn't work, the answer is quite impolite and isn't going to be published here. ;)
These are some ways to approach your problem.
First you could use to name variables directly if you return array of variables that are not part of the collection but have separate meaning each.
Other two ways are for returning the result that is a collection of values.
function test() {
return array(1, 2);
}
list($a, $b) = test();
echo "This should be 2: $b\n";
function test2() {
return new ArrayObject(array('a' => 1, 'b' => 2), ArrayObject::ARRAY_AS_PROPS);
}
$tmp2 = test2();
echo "This should be 2: $tmp2->b\n";
function test3() {
return (object) array('a' => 1, 'b' => 2);
}
$tmp3 = test3();
echo "This should be 2: $tmp3->b\n";
Extremely ghetto, but, it can be done using only PHP. This utilizes a lambda function (which were introduced in PHP 5.3). See and be amazed (and, ahem, terrified):
function foo() {
return array(
'bar' => 'baz',
'foo' => 'bar',
}
// prints 'baz'
echo call_user_func_array(function($a,$k) {
return $a[$k];
}, array(foo(),'bar'));
The lengths we have to go through to do something so beautiful in most other languages.
For the record, I do something similar to what Nolte does. Sorry if I made anyone's eyes bleed.
After further research I believe the answer is no, a temporary variable like that is indeed the canonical way to deal with an array returned from a function.
Looks like this will change starting in PHP 5.4.
Also, this answer was originally for this version of the question:
How to avoid temporary variables in PHP when using an array returned from a function
Previously in PHP 5.3 you had to do this:
function returnArray() {
return array(1, 2, 3);
}
$tmp = returnArray();
$ssecondElement = $tmp[1];
Result: 2
As of PHP 5.4 it is possible to dereference an array as follows:
function returnArray() {
return array(1, 2, 3);
}
$secondElement = returnArray()[1];
Result: 2
As of PHP 5.5:
You can even get clever:
echo [1, 2, 3][1];
Result: 2
You can also do the same with strings. It's called string dereferencing:
echo 'PHP'[1];
Result: H
If it is just aesthetic, then the Object notation will work if you return an object. As far as memory management goes, no temporary copy if made, only a change in reference.
Short Answer:
Yes. It is possible to operate on the return value of a function in PHP, so long as the function result and your particular version of PHP support it.
Referencing example2:
// can php say "homer"?
// print zoobar()->fname; // homer <-- yup
Cases:
The function result is an array and your PHP version is recent enough
The function result is an object and the object member you want is reachable
There are three ways to do the same thing:
As Chacha102 says, use a function to return the index value:
function get($from, $id){
return $from[$id];
}
Then, you can use:
get($foo->getBarArray(),0);
to obtain the first element and so on.
A lazy way using current and array_slice:
$first = current(array_slice($foo->getBarArray(),0,1));
$second = current(array_slice($foo->getBarArray(),1,1));
Using the same function to return both, the array and the value:
class FooClass {
function getBarArray($id = NULL) {
$array = array();
// Do something to get $array contents
if(is_null($id))
return $array;
else
return $array[$id];
}
}
Then you can obtain the entire array and a single array item.
$array = $foo->getBarArray();
or
$first_item = $foo->getBarArray(0);
Does this work?
return ($foo->getBarArray())[0];
Otherwise, can you post the getBarArray() function? I don't see why that wouldn't work from what you posted so far.
You could use references:
$ref =& myFunc();
echo $ref['foo'];
That way, you're not really creating a duplicate of the returned array.